Yes, but he doesn't have any levels in the assassin class. Although keeping death attack Int based does help him with a high Int, it's also boosted by the fact that, as a monster, the DC is also based on his total HD. Of course, what we want is a crazy high DC, so it works out.
I'd reverse the Str and Con scores, as he's going to want Weapon Finesse anyway and will do much more horrible things with his attacks then a few points of bonus Str damage.